Single crystal silicon carbide is very promising in the application of new generation electronic substrates due to its excellent optical, electrical, and thermal properties, such as high breakdown voltage, wide energy gap, high electron drift velocity, and high thermal conductivity, etc.
At present, physical vapor transport (PVT) method is the mainstream technology for growing silicon carbide crystals, which utilizes high purity silicon carbide powder as a raw material. The silicon carbide powder is sublimated at a temperature higher than 2000° C., and the sublimated gaseous molecules are deposited on a low-temperature crystal seed through a temperature field, thereby growing the crystal. The silicon carbide powder serves as the raw material in crystal growth, and its quality directly influences the properties of the crystal that is grown. The purity of the silicon carbide powder is normally considered, because the impurities in the powder will be transferred into the crystal during crystal growth, so as to induce defects in the silicon carbide crystal and affect the electrical properties of the crystal. In addition, the powder topography is one of the factors that will affect crystal growth, and the powder diameter is the key factor for determining the stability and speed of crystal growth.
In general, currently, there are two methods to produce the silicon carbide powder, one is the Acheson method, in which silicon oxide reacts with petroleum coke at a temperature of at least 2500° C. to form a silicon carbide bulk. The bulk is physically crushed and ground to form silicon carbide powder. While the bulk is grown in the atmosphere, it is difficult to control the purity. The purity of the powder is limited by the abrasive contamination during the grinding process. The other method is chemical vapor deposition (CVD), which uses a high purity silicon precursor and a high purity carbon precursor (e.g. SiH4 and C3H8) gases under a vacuum environment. The gaseous molecules of the precursors are decomposed and then react to form silicon carbide powder. The gaseous precursor materials used in this method are of a high purity, so that the silicon carbide powder is also with high purity. However, the powder diameter is too small, so that the crystal growth process becomes difficult. In addition, the yield of the synthesized powder by the CVD method is low, and the cost is too high to be easily commercialized.
Accordingly, an innovative method for manufacturing silicon carbide micropowder is called for.